Laboratory investigation

fatigue loading, the slope of the cephalad L-3 endplate was monitored with a goniometer. The slope at maximum loading every 1000 cycles was compared with the initial slope. If the change in maximum loading slope exceeded 20°, the test was stopped and was noted as failure. The cycle count to failure was recorded for each specimen. Following fatigue loading, each specimen was subjected to FE ROM testing to evaluate the stability of the construct postfatigue. This simulated a significant change in lower lumbar angulation, which could impact standing sagittalalignment

bodies from C-2 to C-7 and then summing the segmental angles for an overall cervical curvature angle.
Translation of the cervical spine in the sagittal plane is measured through the cervical SVA, for which there are different methods of measurement. Both C-2 SVA ( Figs. 2 and 3 left ) and C-7 SVA have been used to define sagittalalignment globally by measuring the distance between the C-2 and C-7 plumb lines, respectively, from the posterior superior corner of the sacrum. Cervical SVA can also be defined regionally using the distance between a plumb line dropped

Darryl Lau, Joseph A. Osorio, Vedat Deviren and Christopher P. Ames

. 13 It has been established that global sagittalalignment and coronal spinal alignment are strongly correlated with functional disability and pain outcomes, as has been validated by various health-related quality of life scores (HRQLS)—greater imbalance leading to greater functional disability. 12 , 14 , 21 , 39 Fortunately, the surgical correction and reestablishment of age-appropriate global spinal alignment and spinopelvic parameters have been demonstrated to significantly improve patient function, pain, and appearance. 19 , 29 , 36 In general, the objective

posterosuperior corner of the C-7 vertebral body. The horizontal line with an arrow represents the C2–7 SVA.
Given the significant impact of sagittalalignment on HRQOL among patients with thoracolumbar spinal deformities, and the studies of Tang et al. 54 and Smith et al. 45 demonstrating correlations between cervical sagittalalignment and multiple measures of HRQOL, the C2–7 SVA was selected as a modifier for the CSD classification. Based on regression analysis from Tang et al., a C2–7 SVA threshold of 4 cm was found to correlate with moderate disability based on the

fracture, the retrospective study suggested that residual postoperative sagittal malalignment and greater BMI may be associated with greater risk of rod fracture. The present prospective study confirms the added risk of rod fracture with greater BMI and confirms that sagittal spinopelvic alignment may also be a risk factor, but instead of postoperative residual sagittal malalignment, the present study suggests that it is the magnitude of sagittalalignment correction that may be a more important factor.
The findings of the present study demonstrate a markedly higher

A review

posterior, respectively, to the posterosuperior corner of the S-1 vertebral body. The T-1 spinopelvic inclination 30 and the T9SPI are alternative measures of SA. These measures are angles between the vertical plumb line extended from the bicoxofemoral axis and lines drawn from the vertebral body center of T-1 or T-9 to the center of the bicoxofemoral axis ( Fig. 3 right ). Since the T-1 and T-9 inclinations are angles rather than measured lines, they are not prone to radiographic magnification issues. Sagittalalignment is also assessed through regional measures of

(PI), pelvic tilt (PT), lumbar lordosis (LL), pelvic incidence–lumbar lordosis (PI-LL) mismatch, sagittal vertical axis (SVA), coronal vertical axis (CVA), and major curve magnitude. The proportion of patients with sagittalalignment and sagittal malalignment in each of the three groups was noted as well. Patients were considered to be well aligned if their SVA was < 5 cm, their PT was < 20°, and the difference between their PI and LL was < 10°. FIG. 2. Illustrations showing FC-only fusion (L4–S1, A ), sacrum to lower thoracic fusion (T10, B ) and sacrum to upper